Dehydration is either a small problem, or a massive one.
A 10% drop in body water can make you itchy, uncomfortable, and affect short term memory.

Longer-term dehydration can lead to organ failure.
Oh yeah, the body dies.
Wait that means you die.

To lose weight you need to be properly hydrated.
To gain muscle mass, you need to be propped hydrated.
I personally am aiming for a gallon and a half daily.
And it is hard.
However, like ny habit all it takes is work and commitment.